Day of the Dragons 
Enchantment
When this enchantment enters, exile all creatures you control. Then create that many 5/5 red Dragon creature tokens with flying. When this enchantment leaves the battlefield, sacrifice all Dragons you control. Then return the exiled cards to the battlefield under your control.
Legality
standardNOT LEGALpioneerNOT LEGALmodernNOT LEGALlegacyLEGALvintageLEGALcommanderLEGAL